Numerous types of prosthetic mechanical heart valves have previously been employed as replacements for malfunctioning endogenous anatomical heart valves.
In particular, one type of prosthetic mechanical heart valve is that known as a "bileaflet" mechanical valve. Mechanical valves of the bileaflet type typically comprise a pair of flat occluder leaflets pivotally mounted within a ring-like annular valve body. The leaflets will pivotally move, in response to hemodynamic movement of the blood, between an "open" position whereby blood is permitted to flow through the annular valve body in a first direction, and a "closed" position whereby blood is prevented from backflowing in a second direction opposite said first direction.
It is desirable for prosthetic heart valves of the bileaflet type to be constructed in a manner which will minimize or prevent the lodging or stagnation of blood within specific regions of the valve, as such stagnation or lodging of blood may result in thrombus formation and the occurrence of associated thromboembolic complications. In particular, one area where blood cells may tend to lodge or stagnate within the hinge or pivot mechanism the occluder leaflets are attached to the annular valve body. Accordingly, some valves of the prior art have incorporated modified pivot/hinge mechanisms purportedly capable of carrying out a self-clearing or self-"washing" function to remove any lodged or stagnating blood cells from the hinge or pivot mechanism.
Additionally, it is desirable for bileaflet mechanical prosthetic valves to be designed such that the leaflets will open and close softly, without slamming or unnecessary surface-to-surface contact, so as to minimize the likelihood of hemolysis (i.e., the breaking or rupture of blood cells).
Furthermore, it is desirable that heart valves of the bileaflet type be configured and constructed to withstand long term usage and wear, without fatigue, breakage or fracture of the valve components.
Examples of prosthetic mechanical heart valves of the prior art include those described in the following U.S. Pat. Nos.: 4,178,639 (Bokros), 4,272,854 (Bokros), 4,276,658 (Hanson, et al.), 4,328,592 (Klawitter), 4,363,142 (Meyer), 4,373,216 (Klawitter), 4,443,894 (Klawitter), 4,451,937 (Klawitter), 4,605,408 (Carpentier), 4,446,577 (Meyer, et al.), 4,676,789 (Sorensen, et al.), 4,692,165 (Bokros), 4,822,353 (Bokros), 4,863,458 (Bokros), 4,863,459 (Olin), 4,872,875 (Hwang), 4,888,010 (Bokros), 4,892,540 (Vallana), 4,923,465 (Knoch, et al.), 4,935,030 (Alonso), 4,995,881 (Knoch, et al.), 5,002,567 (Bona, et al.), 5,061,278 (Bicer), 5,078,738 (Couetil), 5,108,425 (Hwang), 5,116,366 (Hwang), 5,116,367 (Hwang, et al.), 5,123,920 (Bokros), 5,137,532 (Bokros, et al), 5,147,390 (Campbell), 5,152,785 (Bokros, et al.), 5,171,263 (Boyer, et al.), 5,178,632 (Hanson), 5,192,309 (Stupka, et al.), 5,192,313 (Budd, et al.), 5,197,980 (Gorshkov, et al.), as well as the following foreign patents and foreign patent publications: EP238181A, WO 86/05383, WO 91/11973, 0091746, 0465383A1, 0541215A1, WO 92/21305, 0023797, GB2055,452A, 0050439, GB2018396A, 0515324A1, WO92/02197, 0327790, EP289494, EP133608A, WO93/01767, EP89104A, EP256047A, EP436420A, EP 403649A, WO90/04367, EP176237A, and WO91/05524.
Although the prior art has included numerous surgically implantable bileaflet mechanical heart valves, there remains a need in the art for new or improved bileaflet mechanical valves capable of long term, cardiac functioning with minimal likelihood of thromboembolic complications or other untoward side effects.